This invention relates to packaging methods and apparatus, and more particularly to a method and apparatus for forming at least one longitudinal crease in the tube of packaging material in a vertical form, fill and seal packaging apparatus to facilitate formation of packages with a rectangular cross section and/or with flat ends.
For many years, flat bottom packages have been formed from a tube in a vertical form, fill and seal packaging apparatus. In such apparatus score lines are sought to be formed in the advancing tube by applying pressure to the tube with grooved rollers pressing the film of the tube against a sharp corner of an internal guide over which a tube is passing, a process known as scoring. While such apparatus produces lines of weakness in the film which will fold along these lines of weakness, under certain conditions the film is mechanically ruptured with this method. Under any circumstance the film along these score lines is degraded and the barrier properties of the film reduced. If too much pressure is applied, since a relatively sharp corner is used for application of pressure against the film, the film can weaken to the point of severing along the score line.
The present invention eliminates these undesirable conditions by folding the packaging material back onto itself i.e. 180 degrees and ironing in the crease, similar to folding a piece of paper back over itself and running the paper between finger and thumb. Any weakening of packaging material by this method is only that inherent in the material itself.
Vertical form, fill and seal apparatus has been used for many years. For example, U.S. Pat. No. 4,288,965, the disclosure of which is incorporated herein by reference, relates to one type of form, fill and seal apparatus and process for a web of flexible plastic material. In this apparatus, the web is guided over a forming shoulder to form the web into a tube. The tube is then fed intermittently downwardly over an internal guide, longitudinally sealed at its bottom, filled with a product, and then sealed and severed into individual packages each containing a measured quantity of the packaged product. U.S. Pat. No. 4,288,965 is assigned to Hayssen Manufacturing Company, assignee of the present application and assignee of many patents and applications relating to such methods and apparatus.